Geographic Range
Megamouth sharks (
Megachasma pelagios
) are found in shallow coastal and open-water pelagic waters. Their range is believed
to span the region between latitudes of 40°N and 40°S. These sharks inhabit the Atlantic,
Indian, and Pacific oceans.
Confirmed sightings or catches include coastal regions of the countries of the United
States (Hawaii and San Diego, Catalina Island, San Clemente, California), Australia,
Brazil, Indonesia, Japan, the Philippines, Taiwan, Senegal, Vietnam, Sri Lanka, South
Africa, Peru, China, and Ecuador.
- Biogeographic Regions
- nearctic
- oriental
- neotropical
- australian
- indian ocean
- atlantic ocean
- pacific ocean
- Other Geographic Terms
- cosmopolitan
Habitat
Megamouth sharks are found in deep, warm oceanic water. Megamouth sharks have been caught at depths of around 600m. These sharks move vertically through the water according to the migration of their prey, which follows the light cycle. Megamouth sharks swim deeper during the day and closer to the surface nocturnally. At night, megamouth sharks are found at depths between 150m and 500m. During the day, megamouth sharks swim at depths between 350m and 600m. Kyne et al. (2019) list the full range of depths from 5m to 1500m below the surface.
Campagno (2002) reported data from one radiotracked shark, finding that in 2 days,
it traveled vertically multiple times. At dusk, it was at depths of just 12-25m below
the surface, and 120-166m at sunrise. During daylight hours, to moved to 700-850m
below the surface. Speeds of travel were 1.5-2.1 km per hour, regardless of time of
day.
- Habitat Regions
- saltwater or marine
Physical Description
Megamouth sharks earned their name due to their massive mouth. These sharks have a large terminal mouth and distinct short, round snout. The jaw of megamouth sharks extends past the eyes. The ventral side of megamouth sharks is white, and the dorsal side is grey. Megamouth sharks have dark spots under their lower jaws. Megamouth sharks have a series of small hooked teeth along their top and bottom jaws. Megamouth sharks have two pointed dorsal fins, two tapering pectoral fins, a relatively small pelvic fin, and a small, pointed anal fin.
Male megamouth sharks are typically 425- 515 cm long. Female megamouth sharks are
usually above 500 cm long. Female megamouth sharks are larger than males with the
largest recorded female measuring 544 cm and 1,040 kg. Another female was reported
as "ca. 550 cm" by Nakaya (2001). A juvenile male megamouth shark was caught off the
coast of Brazil. It weighed 24.4kg and was 190 cm in length.
- Other Physical Features
- ectothermic
- bilateral symmetry
- Sexual Dimorphism
- female larger
Development
The stages of development are not entirely known. No female megamouth sharks with
embryos or newborns have been caught. What is known is available is due to by-catches
by fishermen and strandings.
Female megamouth sharks are not fully mature until they reach about 5m in length.
Males megamouth sharks fully mature at about 4 m in length. More specifically, 50%
of female megamouth sharks are mature at 5.17 m, and males at 4.26 m. Megamouth sharks
are thought to be less than 177 cm at birth. Megamouth sharks are thought to exhibit
indeterminate growth, as do all sharks.
- Development - Life Cycle
- indeterminate growth
Reproduction
Little research has found anything conclusive about megamouth sharks' mating systems.
However, some female megamouth sharks have been caught with fresh or healing mating
scars, and male megamouth sharks have been caught with spermatophores coming from
their claspers. The presence of claspers and spermatophores indicates internal fertilization
from the males. Mating scars indicate a form of marking or biting of females.
- Mating System
- polygynandrous (promiscuous)
Megamouth sharks are ovoviviparous and show signs of oophagy (eating their own eggs). Fertilization is internal, with males using claspers for fertilization. The number of offspring is unknown. It is believed that megamouth sharks give birth to large offspring in small numbers. Mass at birth and gestation period is unknown. Megamouth sharks are thought to be less than 177 cm at birth. A juvenile caught off the coast of Brazil weighed 24.4kg and was 190cm in length.
It is thought that megamouth sharks mate year-round and give birth near the equator based on the locations that few juveniles have been caught.
Sexual maturity appears to be based on length, as ages are not reported. Female megamouth
sharks are not fully mature until they reach about 5m in length. Males megamouth sharks
fully mature at about 4 m in length. More specifically, 50% of female megamouth sharks
are mature at 5.17 m, and males at 4.26 m.
- Key Reproductive Features
- iteroparous
- sexual
- fertilization
- ovoviviparous
The extent of parental investment in megamouth sharks is not known. Being ovoviviparous,
the eggs remain in the female while they develop, providing a type of protection until
hatching. Males exhibit no parental investment beyond the act of mating.
- Parental Investment
- female parental care
-
pre-hatching/birth
-
protecting
- female
-
protecting
Lifespan/Longevity
The lifespan and longevity of megamouth sharks is unknown due to the lack of sightings.
However, basking sharks (
Cetorhinus maximus
), which researchers believe should belong in the same family as megamouth sharks,
have a similar morphology to megamouth sharks and have a lifespan of about 50 years.
It is suspected that megamouth sharks have a similar lifespan. These sharks are not
kept in captivity.
Behavior
Megamouth sharks move vertically through the water, being caught at deeper depths during the day, and more shallow depths at night, and are slow, crepuscular swimmers. This behavior likely occurs as megamouth sharks are following the movement of emphasiid shrimps and copepods.
Campagno (2002) reported data from one radiotracked shark, finding that in 2 days, it traveled vertically multiple times. At dusk, it was at depths of just 12-25m below the surface, and 120-166m at sunrise. During daylight hours, to moved to 700-850m below the surface. Speeds of travel were 1.5-2.1 km per hour, regardless of time of day.
Megamouth sharks have also been caught with mating scars and claspers. These indicate
internal fertilization by the male. Beyond what is known from strandings and by-catches,
not much else is reported about the behavior of these sharks. They are suspected to
be solitary, not known to travel in groups.
- Key Behaviors
- natatorial
- crepuscular
- motile
- migratory
- solitary
Home Range
Communication and Perception
Not much is known about how megamouth sharks specifically communicate with each other. Like other sharks, megamouth sharks have eyes that include key features found in most vertebrates including the retina, a cornea, and an iris, they also have a tapetum lucidum, which allows them to see in darker waters. As with all sharks, megamouth sharks have both a lateral line and ampullae of Lorenzini. The lateral line aids sharks in recognizing the presence of both predators and prey. The ampulla of Lorenzini uses electrical fields to detect prey.
Megamouth sharks also have a white band on their top jaw. Nakaya (2001) believed
it functioned in two ways - as a lure for plankton in low-light conditions, and as
a way for conspecifics to recognize one another (because it appears to be unique to
megamouth sharks).
Food Habits
Megamouth sharks are planktotrophic, mostly eating krill. More specifically, megamouth sharks eat shrimp from the family Euphausiidae and copepods. Occasionally, they consume jellyfish, including the species Atolla vanhoeffeni . Stomach contents from a shark in Hawaiian waters found primarily a euphausiid shrimp, Thysanopoda pectinata . In Japan, the shrimp species consumed there was tentatively identified as Euphausia nana .
Megamouths sharks are typically caught in deeper waters in the day and are found closer
to the surface at night, following the movements of their prey. During the day, megamouth
sharks are caught in oceanic waters at depths around 350m and 600m, at night they
are caught around 150m and 500m.
- Primary Diet
-
carnivore
- eats other marine invertebrates
- planktivore
- Animal Foods
- aquatic crustaceans
- zooplankton
- Foraging Behavior
- filter-feeding
Predation
The only recorded predator of megamouth sharks is cookiecutter sharks (
Isistius brasiliensis
). In 1998, three sperm whales (
Physeter catodon
) were seen attacking a 5-m-long megamouth shark in Indonesian waters. Humans (
Homo sapiens
) also catch megamouth sharks in occasional bycatch incidents.
Ecosystem Roles
Megamouth sharks are planktotrophic, feeding on euphausiid shrimps, jellyfish, and
copepods. Predators of megamouth are limited, but may include cookiecutter sharks
(
Isistius brasiliensis
). Parasites of megamouth sharks are pandarid copepods (
Dinemolells indeprenslis
) and tapeworms.
- Copepod ( Dinemolells indeprenslis )
- Tapeworms (Cestoda)
Economic Importance for Humans: Positive
Megamouth shark specimens have been preserved and used for research and educational
purposes. They have also been eaten in some countries where they have been caught
including Brazil, Taiwan, and the Philippines.
- Positive Impacts
- food
- research and education
Economic Importance for Humans: Negative
Although megamouth sharks are not known to pose any direct threats to humans, they
do have the potential to damage or break the fishing nets they are caught in due to
their immense size.
Conservation Status
Megamouth sharks are considered to be a species of "Least Concern" on the IUCN Red List. The US Federal List, CITES, and the State of Michigan List have no special status for megamouth sharks.
Megamouth sharks are typically caught by fisheries in rare bycatch incidents, although they have also been found washed up on shores in Japan and other countries. Many specimens have been caught by fisheries fishing for sharptail mola ( Masturus lanceolatus ). From 2013-2015, 34 megamouth sharks were caught as bycatch. These sharks, by their rarity, would make overexploitation (intentional or not) a serious threat.
Specimens of megamouth sharks are used for displays, research in education. In U.S. waters in the Pacific Ocean, collection had been prohibited since 2004. As of 2015, it is now legal for fisheries to keep a megamouth specimen if it was caught accidentally - but it must be donated to a museum or for research facilities. In other countries such as Taiwan, megamouth sharks must be reported to the government if caught. Kyne et al. (2019) recommend that if megamouth sharks continue increasing in numbers as bycatch of driftnet fisheries in Taiwan and other Asian fisheries, live release should be required.
All that is known about megamouth sharks is based on 124 records; increasing the sample
size without mortality would be a sound step in learning more about the natural history
of this shark.
Additional Links
Contributors
Acalia Carter-Martin (author), Radford University, Karen Powers (editor), Radford University, Victoria Raulerson (editor), Radford University, Christopher Wozniak (editor), Radford University, Genevieve Barnett (editor), Colorado State University.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Australian
-
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Atlantic Ocean
-
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- Pacific Ocean
-
body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- cosmopolitan
-
having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.
- saltwater or marine
-
mainly lives in oceans, seas, or other bodies of salt water.
- pelagic
-
An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).
- coastal
-
the nearshore aquatic habitats near a coast, or shoreline.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- indeterminate growth
-
Animals with indeterminate growth continue to grow throughout their lives.
- polygynandrous
-
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- internal fertilization
-
fertilization takes place within the female's body
- ovoviviparous
-
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
- female parental care
-
parental care is carried out by females
- natatorial
-
specialized for swimming
- crepuscular
-
active at dawn and dusk
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- solitary
-
lives alone
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- electric
-
uses electric signals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- electric
-
uses electric signals to communicate
- zooplankton
-
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
- filter-feeding
-
a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.
- food
-
A substance that provides both nutrients and energy to a living thing.
- carnivore
-
an animal that mainly eats meat
- planktivore
-
an animal that mainly eats plankton
References
Acuña-Perales, N., F. Córdova-Zavaleta, J. Alfaro-Shigueto, J. Mangel. 2021. First records of the megamouth shark Megachasma pelagios (Taylor, Compagno & Struhsaker, 1983) as bycatch in Peruvian small-scale net fisheries. Marine Biodiversity Records , 14/1: 1-7. Accessed September 06, 2021 at https://mbr.biomedcentral.com/articles/10.1186/s41200-020-00198-x .
Alston, A., I. Close, P. Gilbert, P. Goadby, S. Johnson, N. Kemp, N. Otway, J. Pepperell, R. Taylor, V. Taylor, S. Turner. 1986. Sharks: Silent Hunters of the Deep . Surry Hills, Australia: Reader's Digest.
Berra, T., B. Hutchins. 1990. A specimen of megamouth shark, Megachasma pelagios (Megachasmidae) from Western Australia. Record of the Western Australian Museum , 14/4: 651-656.
Castillo-Géniz, J., A. Ocampo-Torres, K. Shimada, C. Rigsby, A. Nicholas. 2012. Juvenile megamouth shark, Megachasma pelagios, caught off the Pacific coast of Mexico, and its significance to chondrichthyan diversity in Mexico. Ciencias Marinas , 38/2: 467-474.
Castro, J. 2010. The Sharks of North America . New York, New York: Oxford University Press.
Compagno, L. 1984. Sharks of the World. An Annotated and Illustrated Catalogue of Shark Species Known to Date . Rome: Food and Agriculture Organization of the United Nations.
Duchatelet, L., V. Moris, T. Tomita, J. Mahillon, K. Sato, C. Behets, M. Jérôme. 2020. The megamouth shark, Megachasma pelagios, is not a luminous species. PLoS ONE , 15/11: e0242196. Accessed September 06, 2021 at https://doi.org/10.1371/journal.pone.0242196 .
Dulvy, N., J. Reynolds. 1997. Evolutionary transitions among egg-laying, live-bearing and maternal inputs in sharks and rays. Proceedings of the Royal Society of London, Series B: Biological Sciences , 264: 1309-1315.
Dulvy, N., S. Fowler, J. Musick, R. Cavanagh, P. Kyne, L. Harrison, J. Carlson, L. Davidson, S. Fordham, M. Francis, C. Pollock, C. Simpfendorfer, G. Burgess, K. Carpenter, L. Compagno, D. Ebert, C. Gibson, M. Heupel, S. Livingstone, J. Saciangco, J. Stevens, S. Valenti, W. White. 2014. Extinction risk and conservation of the world's sharks and rays. eLife , 3: e00590. Accessed November 19, 2021 at https://elifesciences.org/articles/00590 .
Dulvy, N., C. Shelley, J. Baum, E. Cortés. 2008. You can swim but you can't hide: The global status and conservation of oceanic pelagic sharks and rays. Aquatic Conservation Marine and Freshwater Ecosystems , 18/5: 459-482.
Ebert, D., S. Fowler, L. Compagno. 2013. Sharks of the World A Fully Illustrated Guide . Plympton, United Kingdom: Wild Nature Press.
Eschmeyer, W., J. Paxton. 1998. Encyclopedia of Fishes . San Diego, California: Academic Press.
Honebrink, R., R. Buch, P. Galpin, G. Burgess. 2011. First documented attack on a live human by a cookiecutter shark (Squaliformes, Dalatiidae: Isistiussp.). Pacific Science , 65/3: 365-374.
Ito, H., M. Yoshimoto, H. Somiya. 1999. External brain form and cranial nerves of the megamouth shark, Megachasma pelagios. Copeia , 1999/1: 210-213.
Kazunari, Y., J. Morrissey, Y. Yabumoto, K. Nakaya. 1997. Biology of the Megamouth Shark . Tokyo, Japan: Tokai University Press.
Kyne, P., K. Liu, C. Simpfendorfer. 2019. "Megachasma pelagios" (On-line). The IUCN Red List of Threatened Species 2019: e.T39338A124402302. Accessed November 22, 2021 at https://dx.doi.org/10.2305/IUCN.UK.2019-1.RLTS.T39338A124402302.en .
Liu, K., M. Lee, S. Joung, Y. Chang. 2009. Age and growth estimates of the shirttail mola, Masturus lanceolatus, in waters of eastern Taiwan. Fisheries Research , 95/(2-3): 154-160.
Liu, S., S. Joung, C. Yu, H. Hsu, W. Tsai, K. Liu. 2018. Genetic diversity and connectivity of the megamouth shark (Megachasma pelagios). PeerJ , 6: 4432. Accessed September 06, 2021 at https://doi.org/10.7717/peerj.4432 .
Maisey, J. 1985. Relationships of the megamouth shark, Megachasma. Copeia , 1985/1: 228-231.
MartÃnez-Ortiz, J., D. Mendoza-Intriago, W. Tigrero-Gonzalez, G. Flores-Rivera, R. López-Párraga. 2017. New records of megamouth shark, Megachasma pelagios off Ecuador, Eastern Pacific Ocean. Ciencia Pesquera , 25/2: 27-30.
Nagasawa, K., H. Senou. 2012. Third record of Dinemoleus indeprensus (Copepoda: Pandaridae) from the megamouth shark, Megachasma pelagios. Biogeography , 14: 147-149.
Nakaya, K. 2001. White band on upper jaw of megamouth shark, Megachasma pelagios, and its presumed function (Lamniformes: Megachasmidae). Bulletin of the Faculty of Fisheries, Hokkaido University , 52/3: 125-129.
Parsons, G. 2006. Sharks, Skates, and Rays of the Gulf of Mexico . Mississippi: Mississippi Alabama Sea Grant Program.
Ritter, E., R. Amin. 2019. Mating scars among sharks: evidence of coercive mating?. acta ethologica , 22: 9-16.
Sawamoto, S., R. Matsumoto. 2012. Stomach contents of a megamouth shark Megachasma pelagios from the Kuroshio Extension: Evidence for feeding on a euphausiid swarm. Plankton & Benthos Research , 7/4: 203-206.
Stevens, J. 1999. Sharks . New York, New York: Checkmark Books.
Tomita, T., K. Sato, J. Suda, K. Nakaya. 2011. Feeding of the megamouth shark (Pisces: Lamniformes: Megachasmidae) predicted by its hyoid arch: A biomechanical approach. Journal of Morphology , 272/5: 513-524.
Tomita, T., S. Tanaka, K. Sato, K. Nakaya. 2014. Pectoral fin of the megamouth shark: Skeletal and muscular systems, skin histology, and functional morphology. PLoS ONE , 9/1: e86205. Accessed November 19, 2021 at https://doi.org/10.1371/journal.pone.0086205 .
Watanabe, Y., Y. Papastamatiou. 2019. Distribution, body size and biology of the megamouth shark Megachasma pelagios. Journal of Fish Biology , 95/4: 992-998.
White, W., A. Fahni, K. Sumadhiharga. 2004. A juvenile megamouth shark Megachasma pelagios (Lamniformes: Megachasmidae) from northern Sumatra, Indonesia. Raffles Bulletin of Zoology , 52/2: 603-607.
Yano, K., Y. Yabumoto, S. Tanaka, O. Tsukada, M. Furuta. 1999. Capture of a mature female megamouth shark, Megachasma pelagios, from Mie, Japan. Indo-Pacific Fish Conference: 335-349.
de Moura, J., A. Merico, R. Montone, J. Silva, G. Seixas, J. de Oliveira Godoy, T. Saint'Pierre, R. Hauser-Davis, A. Di Benedetto, E. Reis, D. Tavares, L. Lemos, S. Siciliano. 2015. Assessment of trace elements, POPs, 210Po and stable isotopes (15N and 13C) in a rare filter-feeding shark: The megamouth. Marine Pollution Bulletin , 95/1: 402-406.
Food and Agriculture Organization of the United Nations. Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date, Volume 2. Bullhead, Mackerel and Carpet Sharks (Heterodontformes, Lamniformes and Orectolobiformes). FAO Species Catalogue for Fishery Purposes No. 1. Rome, Italy: Food and Agriculture Organization of the United Nations. 2002. Accessed December 09, 2021 at https://www.fao.org/3/x9293e/x9293e00.htm .